Broadband transmission with high spectrum efficiency and high mobiling velocity (for example, high driving speed) is the essential requirement to future mobile communication systems. The multiple input multiple output (MIMO) technique along with the orthogonal frequency-division multiplexing (OFDM) modulation technique may be the most potential means for achieving foregoing requirement. However, the effect of inter-channel interference (ICI) will become very serious along with the increases of mobiling velocity, carrier frequency, and OFDM symbol time.
When the mobiling velocity exceeds 300 km/h, the signal interference noise ratio (SINR) of an entire communication system is limited by the ICI at 20 dB. As a result, the application of high-order modulation techniques (for example, 16-quardre amplitude modulation (16-QAM) or 64-quardre amplitude modulation (64-QAM)) is restricted. Regarding the future communication systems with high data rate and high mobiling velocity (for example, the Worldwide Interoperability for Microwave Access (WiMAX) system), the mobiling velocity may be up to 350 km/h or even 500 km/h. Accordingly, a MIMO detector and a subchannel interference canceller must be provided, such that a communication system can meet aforementioned requirement.
Presently, many communication equipment manufacturers and research organizations are dedicated to providing a subchannel interference canceller with high performance, high spectrum efficiency, and low complexity, so as to compensate the subchannel interference effect in the future communication systems (for example, the WiMAX system) with high data rate and high mobiling velocity. In addition, with such a subchannel interference canceller with high performance, high spectrum efficiency, and low complexity, a communication system may even adopt a high-order modulation technique, such as aforementioned 16-QAM and 64-QAM. Thereby, a subchannel interference canceller can be applied to any mobile communication system (for example, the WiMAX system and the Digital Video Broadcast-Terrestrial (DVB-T) system) based on the OFDM modulation technique to improve the market competitiveness of a communication electronic product and create a high industrial value.